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Hello all. I recently upgraded from a global g2 to this beautiful Kohetsu hap40 240mm gyuto, this will be my workhorse knife. My understanding is that not all stones will easily put a good edge on this knife because of how hard the steel is. I work professionally in a kitchen and am willing to take it to a stone every few days. I don't think I will need anything much lower than 1000 grit because I never plan on really letting it dull. Can someone more knowledgable recommend me some stones to get and keep a great edge? There are so many options and information out there that my head is spinning a bit trying to really figure it out. I'm willing to spend a bit of money but I can't afford to spend $150+ on a single stone. Thanks a lot.

The good news is you won't need to spend too terribly much to get a decent stone set. Generally, when we refer to stones that would have difficulty with PM steel, we're referring to traditional oil whetstones. Water stones will have much less of an issue with it because they cut much, much faster. Consider the sharpening sets listed, linked here, and hone in on what you might like. I'm really feeling Shapton Pros these days after getting my first, but there are a lot of options out there. We can give specific advice from there if you'd like it.

thickbackzach

Post subject: Re: Kohetsu HAP40 gyuto recommendations?

Posted: Thu Jun 26, 2014 4:49 am

Joined: Thu Jun 26, 2014 4:11 amPosts: 6

That shapton set looks reasonable. Is 4k fine enough grit to be the last stone I use? And do I need a diamond flattener right away or can I wait a few months? I have sharpened my global on a friends stones and since that was 50/50 I did the same amount of stokes on each side. I believe this kohetsu is beveled 70/30 so will I need to do 7 stokes then 3 strokes on the other side?

Lepus

Post subject: Re: Kohetsu HAP40 gyuto recommendations?

Posted: Thu Jun 26, 2014 5:31 am

Joined: Sat Mar 01, 2014 7:15 amPosts: 2159Location: Raleigh, NC

4k is a good working kitchen edge. I like 4k-6k for professional work. As far as sharpening, you're going to sharpen them roughly equally on both sides. You have more metal to abrade on the larger bevel, but you have more knife on the stone at the same time. It evens out. If you sharpened in a 7:3 ratio you'd wear the knife away into a single bevel knife!

Instead of counting strokes, what you really want to do is work on burr formation. When you sharpen the first side of the knife properly*, you get a small lip of extra metal at the edge of the knife called a burr. It's composed largely by what was once the unsharpened side's former cutting edgeThis is the result of wearing down the metal evenly. You then want to flip the knife and sharpen the other side until you, again, get a burr. Once you've raised a burr on both sides, you need to do a little more work to work it down and polish the knife a bit more. Then you go to the finer stone and repeat the process. At this point, both sides are sharp and you'll want to remove the burr, which is the only thing between you and a truly sharp knife. To remove this, you have two options. You can break the burr using a felt block or a cork. Or you can use the stone and stropping to work away the burr gradually, as though it's not there. If you wish you can deburr between stones or at the end. I usually deburr between stones, but it's a personal preference.

Peter Nowlan, someone I very much respect on this forum, made a video of himself doing a knife that he claims is not for educational purposes, but he's mistaken. He discusses a lot of elements that are helpful and dispels a lot of the mysticism that's sadly common. If I could pick one sharpening guru to learn from on here, it would be him.

He also has a terribly useful forum thread that has helped me really solidify what I know about sharpening. This is a link to it.

Ken Schwartz also has a good number of very technical videos that go into great depth, but they're very information heavy. He also takes your phone calls and is a font of sharpening knowledge for the American kitchen and knife community. The videos involve a lot of complex concepts and are factually rich. I'd suggest those after you get a few great knife edges, better than the ones a knife comes with, under your belt. You'll get more out of them.

*I know you don't technically have to form a burr on the initial side, particularly if the knife is terribly dull and you don't want to change the bevel ratio. Please to not shoot me for minor mistakes.

thickbackzach

Post subject: Re: Kohetsu HAP40 gyuto recommendations?

Posted: Thu Jun 26, 2014 5:54 am

Joined: Thu Jun 26, 2014 4:11 amPosts: 6

Wow thank you for the high effort post. Great information. I have a friend with a Norton stone that he only used very briefly before upgrading to some japanese stones. I haven't seen much info on these but it's a 1000/4000 combo stone. Would this be good enough to use on my hap40? I'm willing to spend the money if necessary but considering he's willing to give it to me for like 10 bucks I'm considering taking the cheaper option. Also, do I need to buy a diamond plate for flattening right away?

Lepus

Post subject: Re: Kohetsu HAP40 gyuto recommendations?

Posted: Thu Jun 26, 2014 6:15 am

Joined: Sat Mar 01, 2014 7:15 amPosts: 2159Location: Raleigh, NC

The easy answer first. No, you do not require diamond plates. You can flatten with sandpaper, or other stones, or even a sidewalk (please don't kill me Ken, people do it). The plates are cost effective in the long run, since good ones last decades, but sandpaper is a cheap solution when starting out. 220 grit from 3M is very much up to the task. It's even somewhat reusable, particularly if you have some wet/dry laying around. Sidewalk flattening causes grit contamination and prevents you getting that perfect edge. For $3, sandpaper is worth it.

The Norton stones work, but they're frustrating for beginning sharpeners to use. The chemical compositions of the abrasive and binder used to make the stone are different. Without getting technical, they don't cut as cleanly or offer very good feedback. Many a beginning sharpener has tried to use budget stones or very sharp knives only to get frustrated when they don't get a good edge. You'd be doing your sharpening a big favor if you bought a nicer combo stone instead. King makes a few combo stones that aren't terribly costly and are much better than the Nortons. Link to one here. I would suggest the Imanishi combo stone over it because it's overall nicer for a very slight price increase, but it's out of stock. Link here. That stone may or may not come back into stock quickly, you'd have to ask Mark. If it's not a long way out, it would be a great starting point.

I'll also reveal something that's a common sentiment on knife forums. People almost universally wish they had bought great stones, e.g. Shaptons, Nubatamas, and Choseras, sooner. I caught a little of this; I bought some diamond plates, which work faster than any stone but leave huge scratches and have terrible feedback, before I got into decent waterstones. If you have the ability and you're going to put them to good use, you would be doing yourself a world of good to swallow the high cost and buy some Shaptons to match your fine knife.

It initially hurts a lot to pay $120 for rocks, even if they're special rocks. There are rocks everywhere. But had I done so I'd have saved myself maybe $100 in pretty useless diamond plates (I now use them to flatten my fine grit stones) because I ended up buying nice stones in the end anyway. And if you get high end stones and decide you don't like them very much, someone will buy them from you at minimal loss. The same cannot be said for less costly stones. I can personally promise you I'll buy your Shapton Pro 5k back off you at near market value. High grade sharpening stones and knives retain their value better than some houses.

Link here to what I would buy. The ShaptonGlass stones linked earlier are on par and my preference is based on knowing the Pro line more intimately. Both lines are clear to the point that, if you follow either according to grit, you end up with a lightsaber. Nubatamas tend to be much more nuanced, the sort of set you build over years as you need stones for specific purposes. You might jump grits or change styles to get the exact edge you want. Choseras are ludicrous. I'm sure they grab the knife and sharpen it themselves, but there's no way I as a non-professional can work my head around it.

Last edited by Lepus on Thu Jun 26, 2014 6:37 am, edited 1 time in total.

thickbackzach

Post subject: Re: Kohetsu HAP40 gyuto recommendations?

Posted: Thu Jun 26, 2014 6:27 am

Joined: Thu Jun 26, 2014 4:11 amPosts: 6

Ok, you guys have sold me on the shaptons. The question is, pro or glass? I'm leaning towards the pro because I'd think I'd rather have 5k than 4k, but if someone has a strong argument for the glass I'm open to it. Still waiting for an answer about whether it's a necessity to have a tool to flatten them immediately upon purchasing.

Tall Dark and Swarfy

Post subject: Re: Kohetsu HAP40 gyuto recommendations?

Posted: Thu Jun 26, 2014 6:36 am

Joined: Wed Feb 20, 2013 2:22 amPosts: 1084

I have the Pro and like them. They work well on HAP40. The only reason I linked to glass is because many respected sharpeners prefer them.

You will need to flatten your stones eventually (not upon receipt) and I recommend the DMT XXC. You will have the luxury of time because once you sharpen your HAP40 it will be a while before they need to see the stones again.

Cheers,

Rick

Lepus

Post subject: Re: Kohetsu HAP40 gyuto recommendations?

Posted: Thu Jun 26, 2014 6:45 am

Joined: Sat Mar 01, 2014 7:15 amPosts: 2159Location: Raleigh, NC

I edited the above both for clarity and to answer those very questions as the discussion went on without me. I will add here, since TD&S mentioned it, that Shaptons take forever to dish. Considering how long HAP40 keeps an edge, you could go with sandpaper for a very long time. And I also like the DMT for private sharpening. It beats out the generic Chinese stone big time. Were you a pro I'd advise the Atoma, but I know for a fact DMTs are up to occasional flattening. The Atoma is smoother when used to set a bevel and doesn't stick to the stones as often, but strictly for flattening, I don't mind the sticking every now and then.

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